Household Wastewater Treatment: Assessing Drinking Water Contamination Risk

For each category listed on the left that is appropriate to your situation, click the box under rank 1-4 that best applies. Your "rank number" will then be genrated on the right.

Glossary for this Fact Worksheet

Information for this Fact Worksheet (PDF)

 

Please Select Your County:

Quantity (Addressed in Section 1)
 
Low Risk
(rank 4)
Low-Mod Risk
(rank 3)
Mod-High Risk
(rank 2)
High Risk
(rank 1)
Your Rank
1. Water use Conservative water use (less than 30 gallons per person per day). Good maintenance of water-conserving fixtures. No water softener. Whole house use is much less than design capacity.* Moderate water use (30–75 gallons per person per day). Fair maintenance of fixtures. Some water conservation fixtures. Water softener recharges twice a week or less. Whole house use is less than design capacity.* High water use (75–120 gallons per person per day). Poor maintenance of fixtures. Water softener recharges more than twice a week. Whole house use may exceed design
capacity.*		 Excessive water use (greater than 120 gallons per person per day). Leaking fixtures. No water-conserving fixtures. Whole house use frequently exceeds design capacity.*

 

 
2. Collection of
wastewater		 Separate stormwater collection and drainage away from septic system. No settling of soil near tank or collection system. Effluent pipe more than 100 feet from well. No leakage loss of water from collection system needing treatment. Water draining onto drainfield site. Effluent pipe more than 100 feet from well. Some leakage of water that should be treated. Stormwater ponds over septic tank. Effluent pipe more than 50 feet from well. Leakage loss of water that should be treated (Example-discharge of washing machine water on ground). Settling near tank or collection system. Direct connection from gutters or footing drains to septic system.**

 

 
Boldface type in high risk column: Besides representing a higher-risk choice, this practice violates Idaho law.

*If design capacity of your treatment system is unknown, estimate at 200 gallons per day for a two bedroom home.
**It is illegal for subsurface sewage disposal system to be connected directly to gutters or footing drains.

Quality (Addressed in Section 2)

3. Settleable solids No use of garbage disposal unit in kitchen sink. No disposal of bulky items (disposable diapers,
sanitary napkins) in toilet.		 Minimal use of garbage disposal unit (less than 3 times per week) and no disposal of bulky items in system. Moderate use of garbage disposal unit (3–7 times per week) and little disposal of bulky items in system. Frequent use of garbage disposal unit (more than once per day) or disposal of bulky items in system.

 

 

QUALITY (Addressed in Section 2)

4. Dissolved solids
(household
chemicals)		 Minimal disposal of diluted household chemicals (few cups per week), such as acids, degreasers, or disinfectants. No water softener, or not recharged on site. Careful disposal of diluted household chemicals (few pints per week). Water softener used, recharged on site. Moderate disposal of diluted household
chemicals (few quarts
per week).		 Extensive disposal of diluted household chemicals (gallons per week). Any disposal of
concentrated/undiluted household chemicals.

 

 
5. Floatable solids No disposal of cooking grease or oils into septic system. Oil and grease wiped from cooking utensils before washing. No defects visible.
Approved sanitary seal tightly secured. Well vented but not screened.		 Routine disposal of grease or oils. No attempt to reduce disposal of grease and oil from household, but little generated. Extensive disposal of cooking grease or oils in household septic system.

 

 

Site Characteristics (Addressed in Section 3)
6. Horizontal separation of wastewater treatment and disposal site from water supply Treatment and disposal in municipal treatment facility. On-site treatment and disposal more than 400 feet downslope from well. Treatment and disposal 200–400 feet downslope from well. Treatment and disposal 100–200 feet downslope from well. Treatment and disposal upslope, or less than 100 feet from well on any slope.*

 

 
7. Vertical separation between soil absorption system and bedrock, extremely permeable material or normal high ground water Greater than 6 feet. 4-6 feet, using pressure distribution system. 2.5-4 feet Less than 2.5 feet.

 

 
Boldface type in high risk column: Besides representing a higher-risk choice, this practice violates Idaho law.
*State rules require at least 100 feet of horizontal separation distance.
8. Soil type Porous silt loams, sandy clay loams, or silty clay loams. Loams - silt loams. Medium sands to fine sands - loamy sands. Very gravely, coarse sands; very gravelly, loamy sands. Coarse sand.*

 

 

Treatment And Disposal
9. Septic tank
(A disposal component, such as soil absorption, should also be used as part of your system)		 Multiple compartment tank or tanks in series. No leakage. Checked every 1–2 years and pumped as needed. Baffles in place. Good maintenance. Single compartment tank. No leakage. Checked at least every 3–5 years and pumped as needed. Baffles in place. Good maintenance. Single compartment tank. No known leakage. Delayed maintenance schedule or tank in poor repair. Leakage losses. Tank not pumped and maintenance not performed until
problems develop.

 

 
10. Soil absorption (lateral, mound, bed, seepage pit or drywell, or surface disposal) after septic tank or other treatment system Well-maintained drain field or mound system loaded below design capacity.** Medium to fine-textured soils (silt loam, loam, clay loam) with more than 6 feet to saturated soil, bedrock, or other limitation. Drain field or mound system on coarse-textured soils (sandy loam, sand) with more than 4 feet to saturated soil or limiting layer. Loaded below design capacity.** Well maintained. Drain field or mound system with less than 4 feet to saturated soil or limiting layer. Loaded near design capacity.** Pipe to surface. Field drainage system. Poorly maintained or failed lateral or mound system. System loaded above design
capacity.** Seepage pit.

 

 
11. Unused wells No unused, unsealed wells. Unused wells properly
abandoned and protected according to Idaho specifications.		 Unused wells, more than 100 feet from drinking water well, not properly abandoned. Unused well, less than 100 feet from drinking water well, not properly
abandoned.

 

 
Boldface type in high risk column: Besides representing a higher-risk choice, this practice
violates Idaho law.
*Unsuitable soil type.
**If design capacity of your treatment system is unknown, estimate at 200 gallons per day for a two bedroom home

Treatment And Disposal (continued)

Select the wastewater treatment and disposal components that apply to your site
12. Cesspool --- --- --- Any cesspool or surface discharge of wastewater.

       

 

Septage And Holding Tank Pumpage Disposal (Addressed in Section 4)
13. Septage pumping and disposal Licensed septage hauler. Disposal at approved treatment facility. Licensed septage hauler. Disposal location unknown. Licensed septage hauler. Disposal at a
non-approved site.		 Non-approved septage hauler. Disposal at non-approved site.

 

 

Boldface type in high risk column: Besides representing a higher-risk choice, this practice violates Idaho law.